Generally, for example, with reference to JP-11-28994A, a collision detection device is mounted to a vehicle to detect a collision between the vehicle and a human. In this case, the collision with the human is determined based on a signal waveform outputted from a load sensor or a displacement sensor arranged in a front bumper of the vehicle and a signal waveform outputted from a vehicle velocity sensor. That is, the collision with the human is determined, based on that the signal waveform of the load sensor or the like recovers earlier in the case of the collision between the vehicle and a human than in the case of the collision between the vehicle and a fixed object such as other vehicle, a wall, a tree, and a utility pole.
However, according to JP-11-28994A, in the case where the output waveform of the load sensor or the like is not within a predetermined range, it will be determined that there occurs a collision between the vehicle and the fixed object even when the collision obstacle is the human. That is, it is difficult to detect the collision with the human. Moreover, in the case where the output waveform of the load sensor is within the predetermined range, it will be falsely determined that there occurs the collision between the vehicle and the human when the obstacle is the fixed object having a similar property (e.g., mass or stiffness) to the human.
As disclosed in JP-2005-201658A by the applicant of the present invention, a collision detection device is provided to determine whether or not the collision obstacle is a human by a detection of the temperature of the collision object (which is near or contacts the vehicle) by a temperature detection unit.
Thus, a collision signal will be outputted in the case where it is determined the collision obstacle is the human based on the temperature signal and it is determined that an impact signal is outputted. Therefore, even when there occurs the collision between the vehicle and the fixed object having the similar property (e.g., mass or stiffness) to the human, it will not be determined that the collision obstacle is the human because the determining is performed based on the temperature signal. Thus, the false determining can be restricted.
However, in this case, it is difficult for the temperature detection unit to detect the fixed object which is not a heat source. Therefore, in the case where the vehicle collides with an obstacle (which is nearer to vehicle than detection object of temperature detection unit) other than human being, it will be falsely determined that there occurs a collision between the vehicle and the human in the state where the temperature signal from the temperature detection unit indicates that the detection object is the human.